tapping noice

I recently had an irrigation sytem installed in my yard.
7 zones. Everytime a zone comes on there is a tapping sound the is very noisy at first then calms down to just annoyingly noisy.
Is this water hammer?
Is there any correction for the problem?

This is probably not water hammer. Most likley, it's the noise of the water meter spinning.
Steps to correct.
1. Make sure you are using a 1" line from the meter to the backflow preventer.
2. If your state allows it, Use PEX tubing instead of copper, it's much quieter.
3. Upgrade to a larger meter, 1" meter would be Ideal but your city will probably only allow upgrading to a 3/4"

4. If all else fails, maybe you can re nozzle some of the zones to a lower flow rate. This would be the least desirable option.